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File System Operations Specification

Overview

This specification defines the file system operations that enable users to open, edit, and save files directly from their local filesystem using the modern File System Access API.

Requirements

Core Functionality

Directory Access

  • The system MUST use the File System Access API for direct file operations
  • The system MUST allow users to select a directory for file operations
  • The system MUST cache file handles for subsequent operations
  • The system MUST check for File System Access API support before attempting operations
  • The system MUST provide clear error messages when the API is not supported
  • The system SHOULD provide fallback behavior for unsupported browsers

File Tree Display

  • The system MUST render a file tree from the in-memory directory structure
  • The system MUST display files and folders in a hierarchical structure
  • The system MUST highlight the active file in the tree view
  • The system MUST expand/collapse folders to show or hide contents
  • The system MUST provide visual indicators for file types (icons, colors)
  • The system MUST update the file tree after file system changes
  • The system MUST provide search functionality to filter files by name
  • The system MUST support searching within file paths
  • The system MUST update search results in real-time as users type
  • The system MUST clear search results when the search input is cleared

File Operations

  • The system MUST allow users to open files from the file tree
  • The system MUST load file content into the editor
  • The system MUST track the currently active file
  • The system MUST save file changes back to the original file location
  • The system MUST handle file permission errors gracefully
  • The system MUST verify file handles before operations

Editor Integration

CodeMirror Integration

  • The system MUST use CodeMirror as the underlying editor component
  • The system MUST provide syntax highlighting based on file type
  • The system MUST support common programming languages and file formats
  • The system MUST handle file type detection from file extensions
  • The system MUST allow users to manually select syntax highlighting modes

Editor State Management

  • The system MUST track file modification state (unsaved changes)
  • The system MUST display auto-save indicators
  • The system MUST maintain editor state during file switching
  • The system MUST preserve cursor position and scroll position
  • The system MUST handle unsaved changes when switching files

Text Editing

  • The system MUST provide standard text editing capabilities
  • The system MUST support keyboard shortcuts for common operations
  • The system MUST provide line numbers and code folding
  • The system MUST support tab indentation and auto-indentation
  • The system MUST handle large files efficiently

File System Changes

External Changes

  • The system SHOULD detect when files are modified externally
  • The system MAY prompt users to reload externally modified files
  • The system MUST handle file deletion gracefully
  • The system MUST maintain file handle validity across operations

Error Handling

  • The system MUST handle permission denied errors
  • The system MUST handle file not found errors
  • The system MUST provide user-friendly error messages
  • The system MUST offer retry options for transient failures

Non-Functional Requirements

Browser Compatibility

  • The system MUST work in Chrome/Edge (full File System Access API support)
  • The system SHOULD degrade gracefully in browsers with partial support
  • The system MUST inform users about browser compatibility requirements

Performance

  • File tree rendering MUST complete within 100ms for directories with <1000 files
  • File loading MUST complete within 500ms for files <1MB
  • Editor operations MUST remain responsive with large files (>10MB)
  • Search filtering MUST update within 50ms of user input

Security

  • The system MUST request explicit user permission for directory access
  • The system MUST not access files outside the selected directory
  • The system MUST handle file permission denials appropriately
  • The system MUST not cache file handles beyond the session duration

Usability

  • File tree MUST be easily navigable with keyboard and mouse
  • Active file indication MUST be visually distinct
  • Search functionality MUST be easily accessible
  • Error messages MUST be clear and actionable

Implementation Notes

Component Dependencies

  • FileSystemManager: Handles File System Access API integration
  • EditorManager: Wraps CodeMirror and manages editor state
  • UIManager: Coordinates file tree display and updates

File System Access API

  • Use window.showDirectoryPicker() for directory selection
  • Cache file handles for subsequent operations
  • Check window.showDirectoryPicker !== undefined for API support
  • Handle permission re-prompts when file handles expire

CodeMirror Configuration

  • Load CodeMirror from CDN
  • Configure syntax highlighting modes based on file extensions
  • Enable line numbers, code folding, and auto-indentation
  • Configure theme to match application theme

Testing Considerations

  • Test with various file types (text, code, markdown, JSON)
  • Test with large directories (1000+ files)
  • Test with large files (10MB+)
  • Test file system permissions and error conditions
  • Test external file modifications
  • Test browser compatibility (Chrome, Edge, Firefox, Safari)
  • Test file tree navigation and search functionality
  • Test editor responsiveness with various file sizes